In recent years, organic compounds having semiconducting properties have attracted attention. Among the organic compounds, a polyacene compound such as pentacene and tetracene has been known as an organic semiconductor material due to high carrier mobility thereof for many years. “Carrier mobility” herein is used in a broad sense, including electron mobility and hole mobility.
However, publicly known polyacene compounds have low solubility in a solvent, and therefore it is difficult to form films by an application method, a printing method or the like. Therefore, there is no choice other than a vapor deposition method requiring high manufacturing cost for preparing a device having semiconductor characteristics (hereinafter, also referred to as “device”). Further, the publicly known polyacene compounds also have a problem on chemical stability such as oxidation resistance, and therefore these are difficult materials from a viewpoint of industrial practicality.
Consequently, studies have been carried out on compounds in which various substituents are introduced on an acene skeleton (see Patent literature No. 1 and Non-patent literature No. 1, for example) in order to improve the solubility and the chemical stability. Further, also studies have been already carried out on compounds in which chalcogen such as sulfur and selenium is introduced on a part of an acene skeleton, for example, dibenzothienothiophene (BTBT) and dinaphthothienothiophene (DNTT) (see Patent literature Nos. 2 to 3, for example).
According to the Patent literatures, success has been made in improving the chemical stability in the compounds while high carrier mobility is maintained. However, those compounds have linear and highly symmetrical molecular structure, and therefore have a problem of solubility being not necessarily sufficient even if a substituent such as an alkyl group is introduced thereon, or the like. Moreover, as the molecular structure becomes further complicated, the compounds can be barely synthesized using an expensive raw material or a reactant having a high environmental load, and through multi-step synthesis.
Thus, various kinds of organic compounds having semiconductor characteristics have been developed so far. However, development has not sufficiently been made yet for an organic compound that is easily synthesized, and that has excellent thermal•chemical stability, high solubility in a solvent and high carrier mobility (material that can be applied or printed in a solution state, and can be applied to a wide range of uses, such as transistor preparation).
Therefore, an organic semiconductor material having a nonlinear type structure as a basic skeleton that has a bending part in the molecule have attracted attention in recent years. In regard to the above mentioned organic semiconductor material, the present inventors have already introduced a substituent(s) such as an alkyl group at a specific position(s) on the V- or U-shaped molecule such as dinaphthofuran, dinaphthothiophene, dianthrafuran and dianthrathiophene or the like, and then come to find organic semiconductor materials being excellent at thermal•chemical stability, also having high solubility and high carrier mobility (see non-patent literature No. 2).
As the further research of the above mentioned organic semiconductor material, the present inventors have given attention to kinds of N-shaped molecule having two bending parts in the molecule itself; these are dibenzodichalcogenoacenes, dinaphtodichalcogenoacenes and dianthradichalcogenoacenes.
Also of these N-shaped molecules, several examples have been already disclosed (see Patent literatures Nos. 4-8).
In Patent literatures No. 4-6, there are mentioned regarding dibenzodichalcogenoacene, dinaphtodichalcogenoacene and dianthradichalcogenoacene, and also derivatives of these, organic semiconductor materials and organic films including these compounds, and also their usage.
However in Patent literature No. 4, nothing is proofed about the semiconducting property of the compounds, and also nothing can be found about the effect that comes from introduction of the substituents. In addition, regarding derivatives of the compounds on which one to three alkyl groups or phenyl groups are introduced, the compounds themselves are not disclosed, and also nothing is found about solubility of the compounds to solvents, applicability of solutions including the compounds, nor semiconducting property of the compounds.
Further in Patent literatures 5-6, dinaphtodichalcogenoacen and its derivative are not disclosed, nothing is proofed about the semiconducting property of dibenzodichalcogenoacene and dianthradichalcogenoacene, and also of derivatives of these, and nothing can be found about the effect that comes from introduction of the substituents. In addition, regarding a derivative of dianthradichalcogenoacene on which one to three alkyl groups or phenyl groups are introduced, the compound itself is not disclosed, and also nothing is found about solubility of the compound to solvents, applicability of solutions including the compound, nor semiconducting property of the compound.
Furthermore, in Patent literatures Nos. 7-8, dibenzodicarcogenoacene derivative is disclosed as represented by almost the same formula below, but nothing is disclosed about dinaphtodichalcogenoacen and dianthradichalcogenoacene, and also their derivateves.
In the formula, Y is oxygen or sulfur etc., and X is a substituent of various kinds.
Also as an organic semiconductor material, a benzodithiophene of multi-ring type represented by the following formula is disclosed (see Non-Patent literature No. 3). However, nothing can be found about semiconducting property of the compound, and no proof for its usability as an organic semiconductor material is disclosed.
In the formula, R is —C6H13 or -TIPS (triisopropylsilyl).